UNA DISPOSICION DE CIRCUITO PARA SINCRONIZAR LA FRECUENCIA DE UN OSCILADOR CON RESPECTO A IMPULSOS DE SINCRONIZACION DELA FRECUENCIA DE LINEA COMPRENDIDOS EN SENAL DE TELEVISION.

摘要

In a television signal receiver the synchronizing signal is separated at 2, and applied to a pulse shaper 3 to provide discrete pulses coincident with the synchronizing pulses. These discrete pulses are applied to phase discriminator 4 along with pulses derived from an oscillator 7, controlled by the output of the phase discriminator 4. The oscillator 7 produces a pulse train which is frequency divided in a divide-by-20 stage 8 and a divide- by-2 stage 9 to produce pulses at line frequency which are applied through the normal closed contacts of a switch 11 to the input 6. During the period in the field blanking interval when the pre- and post- equalizing pulses of twice line frequency are present the switch 11 provides a path between the output of divider 8 and input 6 to apply twice line frequency pulses to that input. The action of the switch 11 is controlled by a gate 12 controlled from the television signal. The arrangement accelerates pull-in synchronization of the oscillator 7 during the field blanking period.